sub DESTROY {
   my ($self) = @_;
   
   delete $my_objects{$self};

   # We run the destruction in eval, as Perl sometimes produces an error
   # message "Can't call method "FETCH" on an undefined value" when the
   # destructor is called a second time.
   eval('xs_DESTROY($self)');

   unless ($@) {
      # We must clear internaldata, since Perl calls the destructor twice, but
      # on the second occasion, the XS code has already deallocated internaldata.
      # The XS code has problem with setting values in stored hashes, why we do
      # it. This assignment cannot be in eval, since the STORE method only
      # permits DESTROY to change internaldata.
      $$self{'internaldata'} = 0;
   }
}